The increasing reliance on communication networks to transmit more complex data, such as voice and video traffic, is causing a very high demand for bandwidth. To resolve this demand for bandwidth, communication networks are relying more upon optical fibers to transmit this complex data. Conventional communication architectures that employ coaxial cables are slowly being replaced with communication networks that comprise only fiber optic cables. One advantage that optical fibers have over coaxial cables is that a much greater amount of information can be carried on an optical fiber.
The Fiber-to-the-home (FTTH) optical network architecture has been a dream of many data service providers because of the aforementioned capacity of optical fibers that enable the delivery of any mix of high-speed services to businesses and consumers over highly reliable networks. Related to FTTH is fiber-to-the-business (FTTB). FTTH and FTTB architectures are desirable because of improved signal quality, lower maintenance, and longer life of the hardware involved with such systems. However, in the past, the cost of FTTH and FTTB architectures have been considered prohibitive. But now, because of the high demand for bandwidth and the current research and development of improved optical networks, FTTH and FTTB have become a reality.
A conventional hybrid fiber-to-the-home (FTTH)/hybrid fiber-coax (HFC) architecture has been proposed by the industry. HFC is currently the architecture of choice for many cable television systems. In this FTTH/HFC architecture, an active signal source is placed between the data service hub and the subscriber. Typically, in this architecture, the active source comprises a router. This conventional router typically has multiple data ports that are designed to support individual subscribers. More specifically, the conventional router uses a single port for each respective subscriber. Connected to each data port of the router is an optical fiber which, in turn, is connected to the subscriber. The connectivity between data ports and optical fibers with this conventional FTTH/HFC architecture yield a very fiber intensive last mile. It noted that the terms, “last mile” and “first mile”, are both generic terms used to describe the last portion of an optical network that connects to subscribers. Therefore, the distance of a mile should not to be taken literally.
In addition to a high number of optical cables originating from the router, the FTTH/HFC architecture requires radio frequency signals to be propagated along traditional coaxial cables. Because of the use of coaxial cables, numerous radio frequency (RF) amplifiers are needed between the subscriber and the data service help. For example, RF amplifiers are typically needed every one to three kilometers in a coaxial type system.
The use of coaxial cables and the FTTH/HFC architecture adds to the overall cost of the system because two separate and distinct networks are present in such an architecture. In other words, the FTTH/HFC architecture has high maintenance cost because of the completely different wave guides (coaxial cable in combination with optical fiber) in addition to the electrical and optical equipment needed to support such two distinct systems. Stated more simply, the FTTH/HFC architecture merely combines an optical network with an electrical network with both networks running independently of one another.
One problem with the electrical network in the FTTH/HFC architecture involves cable modem technology which supports the data communications between the data service provider and the subscriber. The data service subscriber typically employs a cable modem termination system (CMTS) to originate downstream data communications that are destined to the subscriber. To receive these downstream data communications, the subscriber will typically use a cable modem that operates according to a particular protocol known in the industry as Data-Over-Cable-Service-Interface-Specification (DOCSIS). The DOCSIS protocol defines service flows, which are identifications assigned to groups of packets by the CMTS for the downstream flows based on an inspection of a number of parameters in a packet.
More specifically, a service flow is media access control (MAC)-layer transport service that provides unique directional transport of packets either to upstream packets transmitted by the cable modem or to downstream packets transmitted by the CMTS. The identifications assigned to groups of packets in the DOCSIS protocol can include parameters such as TCP, UTP, IP, LLC, and 802.1 P/Q identifiers contained in an incoming packet.
Based on these identifications, the CMTS assigns a service flow ID (SFID) to a particular datastream. A service flow typically exists when the CMTS assigns this SFID to a datastream. The SFID serves as the principle identifier in the CMTS for the service flow. A service flow is characterized by at least an SFID and an associated direction.
A SFID is usually assigned when a user wishes to communicate. When the user relinquishes the communications channel, the SFID ceases to exist, and if all sessions are closed, all communications with that particular modem cease. When the modem needs to communicate again, it typically must contend for a timeslot in which is then asks for bandwidth. Thus, there will be some delay before communication can restart. This delay may or may not be noticeable to a user, depending on system loading and the nature of the application.
Communication via cable modem is asymmetrical. That is, the data rate that can be achieved in the downstream direction is greater than that which may be achieved in the upstream direction. This is adequate for certain types of communications, such as web surfing. But it is not efficient for other types of services, such as peer-to-peer file transfer (e.g., digital audio file transfers such as Napster type services), nor is it good for large email attachments. This asymmetrical communication is a consequence of using coaxial cable with the need to restrict return signals to low frequencies.
Accordingly, there is a need in the art for a system and method for communicating optical signals between a data service provider and a subscriber that eliminates the use of coaxial cables and related hardware and software necessary to support the data signals propagating along the coaxial cables. There is also need in the art for a system and method for communicating optical signals between a data service provider and a subscriber that can service a large number of subscribers while reducing the number of connections at the data service hub.
There is also a need in the art for a method and system for handling upstream optical communications that can offer guaranteed bandwidth for each subscriber that is part of the optical network. There is a further need in the art for a system and method that can offer guaranteed bandwidth while using any left over portion of this guaranteed bandwidth by placing it in a pool that is accessible by each subscriber. In other words, there is a need in the art for a system and method that can reclaim guaranteed bandwidth among multiple subscribers and place this reclaimed bandwidth in a pool. Another need exists in the art for a system and method that can process group or aggregated packets with token bucket emulation. A further need in the exists for a system and method that can provide a fair allocation of bandwidth to different subscribers where “fair” has a precise mathematical definition. Another need exists in the art for a system and method that can alleviate communication traffic load on an upstream data path.